In current online machine monitoring systems used for machine protection and fault prediction, a large variety of electronic monitoring devices are available, and each is typically specialized to accommodate a particular type of sensor for a particular monitoring application. Various sensor families include eddy current sensors, seismic sensors, passive magnetic sensors, piezoelectric sensors, Hall-effect sensors, and low frequency sensors. Multiple manufacturers offer a large variety of sensors within each of these sensor families for making protection and prediction measurements, and each manufacturer's sensor typically has its own characteristics related to sensor supply power, sensor signal voltage range, and application, such as those listed in Table 1 below.
TABLE 1Supplycurrent, adjustable (0 to 8 mA)piezo and seismic sensorspowervoltage, adjustable (−22 Veddy current sensorsto −30 V)voltage, fixed +/−15 Vlow frequency sensorsvoltage, fixed +30 VHall effect sensorsSignal−30 V to 0 Veddy current sensorsrange0 V to +30 Vpiezo, passive magnetic,Hall effect−15 V to +15 Vseismic, low frequencysensorsMeasure-static (position,eddy current sensors,menteccentricity)low frequencyappli-dynamic (vibration)eddy current, piezo,cationseismicspeed (speed, key)eddy current, Hall,passive magnetic
Conventionally, for a machine monitoring system to accommodate the multiple sensor types with multiple sensor supply voltage requirements and signal voltage range requirements, multiple sensor power supplies and conditioning circuits are required. Sales and project management would be easier if a single sensor interface could handle all the various sensor types and measurements. Production and procurement would be more cost-effective and the number of devices in stock and their spare parts could be reduced significantly, for device manufacturers and their customers.
What is needed, therefore, is a universal sensor interface that is capable of interfacing with all the various different sensor families needed for machine monitoring.